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CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


Canadian  institute  for  Historical  Microreproductions  Institut  Canadian  de  microreproductions  historiques 

1980 


Technical  Notes  /  Notes  techniques 


The  Institute  has  attempted  to  obtain  the  best 
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images  in  the  reproduction  are  checked  below. 


L'Institut  a  microfilm^  le  meilleur  exemplaire 
qu'il  lui  a  6t6  possible  de  se  procurer.  Certains 
d6fauts  susceptibles  de  nuire  d  la  quality  de  la 
reproduction  sont  notds  ci-dessous. 


0 


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n 


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D 


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D 


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distortion  along  interior  margin)/ 
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de  la  distortion  le  long  de  la  marge 
intdrieure) 


D 


Pages  damaged/ 
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D 
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D 
D 


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Le  titre  de  couverture  manque 


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n 


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Des  cartes  g^ographiques  manquent 


D 


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The  images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  legibility 
of  the  original  copy  and  in  keeping  with  the 
filming  contract  specifications. 


Les  images  suivantes  ont  4t6  reproduites  avec  le 
plus  grand  soin,  compte  tenu  de  la  condition  et 
de  la  nettet6  de  I'exemplaire  film6,  et  en 
conformity  avec  les  conditions  du  contrat  de 
filmage. 


The  last  recorded  frame  on  oach  microfiche  shall 
contain  the  symbol  — »►  (meaning  CONTINUED"), 
or  the  symbol  V  (meaning  "END"),  whichever 
applies. 

The  original  copy  was  borrowed  from,  and 
filmed  with,  the  kind  consent  of  the  following 
institution: 

National  Library  of  Canada 


Un  des  symboles  suivants  apparaTtra  sur  la  der- 
nlAre  image  de  cheque  microfiche,  selon  le  cas: 
le  symbole  — ►  signifie  "A  SUIVRE".  le  symboie 
V  signifie  "FIN". 

L'exemplaire  film6  fut  reproduit  grAce  A  la 
g6n«rosit«  de  l'6tablissement  prAteur 
suivant  : 

Bibliothdque  nationale  du  Canada 


IVIaps  or  plates  too  large  to  be  entirely  included 
in  one  exposure  are  filmed  beginning  in  the 
upper  l«ft  hand  corner,  left  to  right  and  top  to 
bottom,  as  many  frames  as  required.  The 
following  diagrams  illustrate  the  method: 


Les  cartes  ou  les  planches  trop  grandes  pour  dtre 
reproduites  en  un  seul  clich6  sont  filmdes  d 
partir  de  Tangle  supirieure  gauche,  de  gauche  d 
droite  et  de  haut  en  bas,  en  prenant  le  nombre 
d'images  ndcessaire.  Le  diagramme  suivant 
illustre  la  mithode  : 


1 

2 

3 

THE 


ORIGIN    OF    GNEISS 


AND  SOME   * 


OTHER  PRIMITIVE   ROCKS 


By  ROBERT  BELL,  B.A.Sc,  M.D.,  LL.D., 

ASSISTANT  DIKECTOU  OF  THE  GEOLOGICAL  SDKVKY  OF  CANADA,  ROYAL 
COMMISSIONER  ON  THE  MINERAL  RESOURCES  OP  ONTARIO,  ETC. 


[Being  an  Abstract  of  a  Paper  roacj  before  tbo  American  Association  por  the 
Advancement  of  Science  in  Toronto,  August,  1880.] 


rniNTKD   BY 
THE  SALEM   PRESS   rUHMSHINO   AND  PRINTING   CO., 

SALEM,  MASS. 

im, 


TlIK  OUIOIN  OK  GNKISS  AND  SOMK  OTIIEU  riilMITIVK  HOCKS.      By  1)U.  IlOBKKT 

Hkij,,  Assistant  Director  of   the  Geological  Survey  of  Ciumda,  Ot- 
tawa, Cuniida. 

[AnSTIlACT.] 

Gni-.iss  beiiiiL;  proljuhly  the  most  iil)mul!iiit  rock  In  the  crust  of  the  cartli, 
it  is  rather  s!ny;ular  that  {jeolonists  have  not  yet  coine  to  a  general  aiiree- 
nient  as  to  its  usual  process  of  fornialion.  I  say  usual,  for  gneissoid  rocks 
may  be  formed  in  more  ways  than  one.  For  example,  the  jiranltic  mate- 
rials of  some  dykes  are  occasionally  found  to  have  assumed  a  i^ueissoid  fo- 
liation parallel  to  the  walls  of  Hit;  dykes,  hut  no  one  would  pretend  that 
this  was  the  normal  mode  of  formation  of  the  continuous  gneiss  of  half  a 
continent. 

It  is  conceivable  that  a  gneissoid,  or  rather  a  streaked,  api)earance  may 
have  been  developed  in  certain  granitic  or  syenitlc  rocks  by  a  flowing  move- 
ment, while  in  a  plastic  state,  l)nt  such  an  appearance  would,  I  think,  l)e 
only  very  liniited  antl  wouUl  difl'er  from  ortliiiary  gneissic  bedeling.  The 
parallel  mottling  or  clouding  and  isolated  patches  of  a  gneissoid  character 
sometimes  met  with  in  granite  or  syenite  may  even  be  accounted  for  lu 
other  ways  than  from  How  motion. 

The  bedding  of  gneiss  dill'ers  from  the  streaking  of  slags  by  flowing, 
in  I)eing  in  continuous  sheets  wldch  generally  ditter  much  in  composition 
as  well  as  color.  It  is  dilUcult  to  imagine  how  llow-structure  could  com- 
nmnicate  a  distinctly  and  uniformly  bedded  arrangement  throughout  a 
depth  of  about  ten  miles  of  strata  which  is  the  ascertained  thickness  of  one 
section  of  the  Upper  Laurentian  alone.  The  presence  of  enormous  beds  of 
limestone,  traceable  continuously  for  a  hundred  miles  or  more,  in  tlie  midst 
of  these  gneisses  appears  to  me  to  be  fatal  to  the  tlow-structure  theory. 
Pressure  will  not  account  for  the  l)eddingof  the  Laurentian  rocks,  for  no 
amount  of  pressure  would  separate  a  homogeneous  mixture  into  distinct 
beds  consisting  of  tlie  ditferent  minerals.  Or  if  pressure  could  se|)arate 
these  constituents,  why  have  certain  areas  remained  as  granite  or  syenite? 

The  composition  of  different  superimposed  beds  of  gneiss  often  differs 
greatly,  some  being  highly  micaceous,  while  this  mineral  is  scarce  in 
others  lying  above  or  below.  Again,  considerable  thicknesses  may  con- 
sist almost  entirely  cf  felspar,  (piartz  or  hornl)lende  alone.  I  might  men- 
tion in  passing  that  hornblende    Is  a  very  abundant  constituent  of  our 

(227) 


228  SECTION    E. 

gneisses  —  li()riil)k'iide-{;nelHS  Ix'liii,'  sihoiit  iis  coninion  as  the  so-called  typ- 
ical or  inica-KiieisH.  Now  ii  fused  inixturc  of  mateiials  would  uot  separate 
iuto  layers  of  lliedifVorcnt  Inj^rcdieuts,  and  certaiidy  uot  into  such  innii- 
uienil)ie  line  layers  as  in!il<e  up  tiie  inimeuse  tldclvuesses  of  tiicso  fjueisses. 
This  is,  I  tliinlv.  anotlier  fatal  ol))eetion  to  the  al)ove  tlieory.  Tlien  some 
of  the  l)('(ldi'(i  roclis  of  tlie  Laurentiaii  system  l)ear  sucliaclose  resemblance 
to  or  uiay  ratlier  l)e  said  to  l)e  identical  witli  rocl<s  wliicii  we  can  trace  to 
a  clastic  and  even  sedimentary  oriftiu,  that  we  are  forced  to  conclude  that 
they  too  iiave  iiad  a  similar  orijjiu. 

Tlie  Upper  l.aurentian  rociis  are  dillcreutiated  into  l)elts  or  groups  of 
l)eds  wiiidi  can  t»e  traced  over  con8ideral)le  distances  on  tlie  ground  and 
can  tlius  l)e  accurately  mapped.  After  carefully  woriiiiig  out  a  large  area 
in  this  way  Sir  William  Logan  proved  that  the  Upper  Laurentian  strata 
obey  the  ordinary  structural  laws  governing  stratified  rocks  when  thrown 
into  anticlinal  and  synclinal  folds. 

The  lower  liaurentinn  gneisses  cannot  be  so  easily  separated  into  dis- 
tinct belts,  and  limestones  appear  to  be  ab.sentfrom  this  division,  but  many 
of  them  resemble  the  gneisses  of  the  upper  series  so  closely  tliat  it  is  al- 
together liliely  they  liad  a  sindlar  origin.  The  Lower  Laurentian  strata 
are  more  contorted  and  at  tlie  same  time  more  solid  or  massive  than  the 
Upper.  Tliey  also  occupy  a  much  larger  geographical  area.  In  Canada  the 
Upp<.-r  Laurentian  appears  to  l)e  confined  to  a  comparatively  limited  region 
extending  from  Georgian  Bay  eastward  through  the  Ottawa  valley  and 
along  the  north  side  of  the  St.  Lawrence.  It  also  occurs  in  eastern  Lab- 
rador and  perhaps  in  Hudson's  Strait. 

In  the  cotintry  stretching  from  Lake  Huron  to  LakeTemiscandng  at  the 
great  l)end  of  the  Ottawa,  ami  thence  northward  and  in  other  directions, 
we  liave  the  best  known  and  one  of  tlie  lai'gest  areas  of  Iluroniau  rocks  in 
Canada.  Having  worked  on  these  rocks  for  a  number  of  years,  I  have  had 
good  opportunity  for  studying  them  and  I  beg  to  ofl'er  a  few  suggestions 
based  on  these  oljsorvations,  as  to  the  origin  of  gneiss  and  some  other  prim- 
itive rocks. 

In  the  region  referred  to  we  have  vast  (piantithis  of  a  rock  of  which  very 
little  has  hitherto  l)eeii  said  Ity  geologists.  The  late  Mr.  Alexander  Mur- 
ray nieiilioned  certain  varieties  of  it  under  tlio  somewhat  erroneous  name 
of  slate  conglomerates.  It  is  a  grey  or  asli  colored  rock  somewhat  resem- 
bling sandstone,  but  usually  massive  or  not  separated  into  distinct  parallel 
beds.  It  bruises  readily  under  tlie  hammer  and  may  be  easily  broken  or 
scratvlied,  showing  that  it  is  largely  composed  of  softer  material  than 
(juartz.  Tills  rock  as  a  matrix  often  contains  large  numbers  of  angularand 
roumled  fragments  of  all  degrees  of  coarseness  from  the  size  of  pins' 
heads  to  that  of  pease,  walnuts,  a  man's  fist  and  even  boulders.  They 
consist  for  the  most  part  of  reddish  quartz-felspar  rock,  granulite  or  binary 
granite,  but  fragments  of  other  rocks  occur  in  some  varieties. 

In  tlie  specimens  which  I  have  examined  under  the  microscope  tlie  matrix 
is  seen  to  consist  principally  of  angular  grains  of  felspar  and  rounded 
grains  of  quartz  with  a  darker  amorphous  mineral  tilling  the  interspaces. 


OEOLOOY    AND    nEOOKAlMlY. 


229 


Much  of  tills  rock  mijilit  he  called  a  volciiiiic  ash  or  brecclii.  The  por- 
tions which  lire  most  tree  IVoiii  pcljbics  or  (riiLtim-iits  are  like  the  golil- 
heariiij;  "  whin  rock  "  of  the  Nova  Scotia  miners.  Some  of  It  might  be 
called  sandstone,  and  mncli  of  it  passes  t)y  insensible  dei;re('s  into  (piartz- 
Ite.  It  is,  however,  desirable  to  have  a  jjeiieral  name  for  tliis  rock  and  I 
know  of  no  slna;ie  word  widcii  will  better  descril)e  it  than  y:re.vwack6. 
Now  this  greywacke  seems  to  me  to  be  tlie  raw  material  ont  of  which 
some  of  the  other  Ilnroniaii  rocks  of  tliis  reu;ion  have  l)i'en  fornn'd.  And 
from  a  stndy  of  the  transfornnition  of  one  rock  into  another  1  have  come 
to  the  conclusion  tliat  the  oiigins  of  several  kinds  of  crystalline  rocks 
hav(!  points  in  common  and  are  nnitually  dependent  on  one  another  in  a 
larger  measure  than  \f^'  may  have  supposed.  Thus  if  we  can  account  for 
the  origin  of  gneiss  we  shall  liave  incidentally  accounted  for  that  of  some 
other  crystalline  rocks  at  the  same  time. 

Another  rock  which  is  very  common  in  some  parts  of  tlie  area  referred 
to  is  quartz-diorite.  It  presents  consideralile  variety  of  conditions  with 
the  same  constituents,  passing  from  tlit;  purely  crystalline  kind  tlirough 
several  stages  less  or  more  moditieil  liy  water,  as  if  it  had  tlowed  out  un- 
der the  sea  and  been  variously  att'ected  by  the  water  according  to  the  vol- 
ume of  the  rock-nnitter  present;  or  in  other  cases  it  seems  lo  liave  l)ei!n 
entirely  broken  up  and  modilled  by  the  sea,  the  constituents  witliout  the 
addition  of  anything  else  resulting  in  an  aipieons  deposit.  The  (piartz- 
diorlte  is  another  parent  from  whii'h  some  of  tlie  other  lluronian  rocks  are 
derived. 

Hut  to  return  to  the  greywack6,  there  are  plenty  of  examples  in  this 
region  which  sliowthat  it  passes  directly  into  ililfereiit  varieties  of  (luarlz- 
syenite  and  gneiss  and  also  that  these  rocks,  as  well  as  quartzites,  clay- 
slates  and  dolomites  may  Ite  derived  from  it. 

In  tiie  direct  formation  of  gneiss  the  materials  of  the  more  slaty  varie- 
ties of  the  greywacke  in  some  cases  appear  to  separate  somewhat  into 
laminaj  by  a  process  of  segregation.  In  other  cases  they  gather  them- 
selves Into  grains  or  spots  by  a  species  of  concretion.  Tlie  complete  con- 
version of  tliese  into  llnished  gneisses  is  effected  by  a  siiglitiy  further  altera- 
tion through  the  agencies  (whatever  they  may  have  been)  which  have 
produced  the  metamorphism  of  the  crystalline  rocks  in  general. 

On  the  other  hand  the  more  massive  varieties  of  the  greywacke  may  be 
seen  to  change  gradually  into  imperfect  and  then  jierfect  or  thoroughly 
cry.stalliiie  quartz-syenite.  The  process  seems  to  be  largely  due  to  con- 
cretionary action,  both  on  a  small  and  large  scale. 

The  breaking  up  and  nioditlcalion  of  the  materials  of  the  greywack6  by 
water  appear  to  give  rise  to  a  great  variety  of  (piarlzites  on  the  one  hand, 
and  to  clny-slates  on  the  other.  These  materials  may  have  been  thrown 
Into  the  sea  either  as  nind  or  dust  and  become  separateil  anil  deposited  at 
once  in  different  places  as  (luarlz-saiul  anil  clay,  or  the  rock,  after  partial 
or  complete  consolidation,  may  have  become  broken  up  and  reduced  by  the 
action  of  water  so  that  the  qiiartzose  :.  id  the  argillaceous  portions  could 
become  separated  and  each  deposited  by  itself,  to  form  the  quartzites  and 


280  SECTION    F. 

claj'-slatfs,  wlildi  almost  ahviiys  accoinpiiny  ciicli  ollior.  as  well  as  the 
yn'ywackd's  of  this  region.  Tin-  very  fact,  of  llic  associatlun  of  tlicso 
rocks  sii;iy;est.s  a  connection  of  all  llicst;  or  a  ilcpcmlcncc  of  tln'  (jnartzitos 
and  clay-slalcs  upon  tlic  ;;ivy\vack6s.  The  clay-slalus  frtM|iicntly  liavu 
layers  of  liornblcmlc  ilcv<-lopt'(l  In  Miciii  parallel  to  the  heddiiiK. 

The  (luart/.llcs  an?  often  largely  mixed  with  llie  softer  material  of  the 
jjrc'ywackC',  hcin^  in  these  cases  merely  tlie  more  silicious  variellfs  of  this 
ro('k  which  |)ass  hy  ins<'n>i!)le  decrees  into  onliiiary  (piarl/ite.  Tlie  (piartz- 
ile,  iiowever,  is  never  entirely  free  from  dissendnated  particles  of  felspar 
ami  this  mliu'ral  in  a  crystalline  form  may  l)c  present  in  all  pro|)ortions 
up  to  nearly  lialf  the  whole?  mass. 

These  crystalline  j;rains  of  felspar  are  generally  liijht  red  in  color  and 
on  very  ohi  surfaces  they  l)e(;ome  dissolved  out  leaving  little  lioles  or  pits. 
On  slly:litly  weatliered  surfaces  they  assume  an  opacpie  white,  contrasting 
with  tin?  vitreous  lustre  of  llie  (piartzite,  .so  that  tliese  surfaces  have  a 
speckled  appearance.  Where  the  felspar  is  uniforudy  and  thickly  scat- 
tered throiijjh  massive  (|nartzite,  liic  rock  is  really  a  (piart/.-felspar  or 
l)imiry  granite  exce|  '  tliat  it  lias  not  yet  l)ecome  entirely  cryslalliiie  l)Ut 
this  chanf;e  ndjtht  readily  he  accomplisheil  in  time. 

Whert!  tlie  felspar  grains  are  disposed  more  thickly  in  rows  in  cross  sec- 
tion, tlie  rock  looks  very  like  f^neiss  iven  to  tlit?  nakeil  eye,  and  sliil  more; 
so  under  the  ndcroscope ;  and  it  ndj^ht  he  converted  into  this  rock  hy 
more  complete  alteration.  On  the  west  side  of  Lady  Evelyn  Lake  between 
Temayand  Lake  and  the  Montreal  liiver  there  is  a  mountain  ridiie  1,100 
feet  ]iijj;h,lar{^ely  composed  of  this  rock,  standinj?  nearly  on  edjie,  which  a 
casual  ol).>erver  mi^lil  easily  taki;  (or  ;;neiss  altliouiih  on  closer  examina- 
tion it  nniy  be  seen  to  be  of  clastic  nature.  Tlie  (piartziti!  beds  or  quartz- 
ose  jjneisses  of  the  Ui)per  Laurentian  in  the  county  of  Ottawa  often  con- 
tain felspar  jjrains  or  crystals  which  weather  out  just  like  those  of  the 
lluronian  iiuarlzites  and  the  outward  apjx'araiice  of  the  two  rocks  is  so 
similar  that  hard  specimens  could  not  he  distin}<[uished  from  each  other. 

The  curious  varielies  of  moditted  ipiartz-diorite  which  have  been  men- 
tioned are  very  abundant  in  some  i)arts  of  the  region  under  consideration 
— notably  in  the  township  of  Denison.  Extensive  sections  may  be  seen 
made  up  of  beds  of  difl'erent  thicknesses,  l)ut  mostly  thin,  in  each  of  wliicli 
the  quartz  grains  and  the  other  components  have  been  roughly  separated 
from  each  other  by  the  action  of  water.  The  bottom  of  each  bed  con- 
sists almost  entirely  of  rounded  grains  of  quartz ;  but,  as  we  ascend,  these 
become  more  and  more  mixed  with  argillaceous  material  till  at  the  top 
there  is  pure  cluy-slatc.  The  same  arrangement  is  repeated  in  all  the  beds. 
In  the  vicinity  of  tliese  ijcds  there  are  others  entirely  of  quarlzite  and  of 
clay-slate,  which  I  l)elieve  owe  their  origin  to  the  disintegration  of  the 
quartz-diorite  (probal)ly  wlien  in  a  soft  condition)  and  the  separation 
and  transportation  of  the  original  ingredients  by  water.  If  the  thin 
alternating  layers  of  quartz  grains  and  slaty  material  were  completely  met- 
amori)hosed  they  would  result  in  gneiss.  The  rocks  of  this  region  there- 
fore appear  to  show  three  ways  by  whicli  gneiss  may  be  formed,  namely, 


GEOLOGY   AND   CROORAPIIT.  S81 

l)y  the  (Urpct  convorslon  of  tlie  tliin  hoddetl  or  sliity  vnrictles  of  grey- 
Wiuk^',  the  nllciiilioii  of  tlie  niixi'il  (luiiitz  and  felspar  rock  derived  from 
oilier  varieties  of  it  and  the  aileratioii  of  tlie  iiiodilled  (luarlz  diorites.  I 
luive  also  found  a  case  wlierc  wliat  appeared  to  liave  l)een  ii  coniniinuled 
niasH  of  f(!lspar  and  decomposed  horiil)lende  wliicli  may  have  lieen  derived 
from  diorile  was  separatin;;  into  interrupted  layi-rs  of  pure  felspar  with 
others  of  schist  which  by  further  alteration  wouUl  form  a  rock  like  f;iieiss. 

The  clay  slates  associated  witli  the  greywack6s  are,  in  some  parts  of  the 
rejjion,  black  or  nearly  so.  On  the  Onapiiij;  river  these  may  be  traced 
into  a  l)lack  breccia  wliii  h  is  clearly  of  volcanic  oii;jin,  largely  developed 
near  ()Ma])in;;  station  on  the  Canadian  Pucilh;  Hallway,  whicli  would  show 
that  the  black  color  in  Huronian  slates  is  not  necessarily  organic  and  that 
any  theory  baseil  on  the  supposition  that  it  is  so  may  i)e  erroneous. 

Tlie  dolomites  of  this  rejiion  are  eviilently  in  most  cases  of  a  concre- 
tionary or  segrejiatcd  mitnrc,  and  have  probably  been  derived  from  the 
decomposition  of  the  honibleiide  or  tlie  aup;ite  of  the  rocks  with  which 
lliey  are  associated.  Small  unstratiHed  masses  of  this  rock  are  not  un- 
coinmoii  111  tlie  diorites,  syenites  and  ;ireywackt's  where  they  have  been 
formed  in  situ,  while  the  layers  and  stratilled  deposits  may  have  been  pre- 
cipitated from  waters  which  carrieil  tiie  carbonates  of  liiiie  and  ina};iiesiii 
to  short  distances  from  the  hornbleiidic  or  auj^itic-beariiig  rocks  undergo- 
ing decomposition. 

During  the  process  of  converting  the  grey  wacke  into  .syenite,  the  difl'used 
iron  which  it  contained  lias  been  ;;atliered  either  into  great  numi)ers  of 
strings  or  small  veins  of  magnetite  or  into  a  lew  larger  ones  of  the  same 
ore  which,  however,  I  have  never  seen  wide  enough  to  be  worked.  Vein.s 
of  this  kind  are  interesting  us  showing  tlie  probability  of  the  formation 
of  more  extensive  larger  ones  of  iron  oxides  witliout  the  existence  of 
organic  life  as  a  means  for  the  concentration  of  tlie  metal. 

Tlie  above  notes  touch  on  nearly  all  the  stratified  and  some  of  the  un- 
stratiHed rocks  of  this  Huronian  region  and  it  is  hoped  that  they  may  iiave 
suggested  some  jjoints  of  interest  for  discussion. 

SALGH  rUESS  I'UBLISHINO  AND  rKINTINO  CO. 


